Podocyte specific knock out of selenoproteins does not enhance nephropathy in streptozotocin diabetic C57BL/6 mice

<p>Abstract</p> <p>Background</p> <p>Selenoproteins contain selenocysteine (Sec), commonly considered the 21^stgenetically encoded amino acid. Many selenoproteins, such as the glutathione peroxidases and thioredoxin reductases, protect cells against oxidative stress by functioning as antioxidants and/or through their roles in the maintenance of intracellular redox balance. Since oxidative stress has been implicated in the pathogenesis of diabetic nephropathy, we hypothesized that selenoproteins protect against this complication of diabetes.</p> <p>Methods</p> <p>C57BL/6 mice that have a podocyte-specific inability to incorporate Sec into proteins (denoted in this paper as PodoTrsp^-/-) and control mice were made diabetic by intraperitoneal injection of streptozotocin, or were injected with vehicle. Blood glucose, body weight, microalbuminuria, glomerular mesangial matrix expansion, and immunohistochemical markers of oxidative stress were assessed.</p> <p>Results</p> <p>After 3 and 6 months of diabetes, control and PodoTrsp^-/-mice had similar levels of blood glucose. There were no differences in urinary albumin/creatinine ratios. Periodic acid-Schiff staining to examine mesangial matrix expansion also demonstrated no difference between control and PodoTrsp^-/-mice after 6 months of diabetes, and there were no differences in immunohistochemical stainings for nitrotyrosine or NAD(P)H dehydrogenase, quinone 1.</p> <p>Conclusion</p> <p>Loss of podocyte selenoproteins in streptozotocin diabetic C57BL/6 mice does not lead to increased oxidative stress as assessed by nitrotyrosine and NAD(P)H dehydrogenase, quinone 1 immunostaining, nor does it lead to worsening nephropathy.</p

Glutamate Induces Mitochondrial Dynamic Imbalance and Autophagy Activation: Preventive Effects of Selenium

Glutamate-induced cytotoxicity is partially mediated by enhanced oxidative stress. The objectives of the present study are to determine the effects of glutamate on mitochondrial membrane potential, oxygen consumption, mitochondrial dynamics and autophagy regulating factors and to explore the protective effects of selenium against glutamate cytotoxicity in murine neuronal HT22 cells. Our results demonstrated that glutamate resulted in cell death in a dose-dependent manner and supplementation of 100 nM sodium selenite prevented the detrimental effects of glutamate on cell survival. The glutamate induced cytotoxicity was associated with mitochondrial hyperpolarization, increased ROS production and enhanced oxygen consumption. Selenium reversed these alterations. Furthermore, glutamate increased the levels of mitochondrial fission protein markers pDrp1 and Fis1 and caused increase in mitochondrial fragmentation. Selenium corrected the glutamate-caused mitochondrial dynamic imbalance and reduced the number of cells with fragmented mitochondria. Finally, glutamate activated autophagy markers Beclin 1 and LC3-II, while selenium prevented the activation. These results suggest that glutamate targets the mitochondria and selenium supplementation within physiological concentration is capable of preventing the detrimental effects of glutamate on the mitochondria. Therefore, adequate selenium supplementation may be an efficient strategy to prevent the detrimental glutamate toxicity and further studies are warranted to define the therapeutic potentials of selenium in animal disease models and in human

THE ANTIOXIDANT CAPACITY OF MILK - THE APPLICATION OF DIFFERENT METHODS in vitro AND in vivo.

Milk contains a wide array of compounds with established or putative pro— or anti—oxidant function. The functions of these compounds have been intensively studied. This review focusses on some important aspects in this wide field namely the methodology for measurement of the total antioxidant capacity (TAC), the content of TAC and some related compounds in human and animal milks and infant formulas, and the effect of milk intake on antioxidant status in the body and on the activity of dietary flavonoids as studied in vitro and in vivo. Regarding methodology TAC in milk can be measured by spectrophotometric and electrochemical methods and some of their characteristics are reviewed. Milk, whey, high—molecular—weight and low—molecular—weight (LMW) fractions of whey have all been found to have antioxidant capacity using these techniques. The major antioxidant in the LMW fraction has been identified as urate. An extensive literature survey was made regarding data on the antioxidant capacity and related variables of milk obtained from different sources (human milk, infant formulas and animal milk) and subjected to different treatments. Differences in TAC between milks from different sources have been observed but due to the variety of techniques used no clear pattern is evident at present. Another important aspect is the putative effects of the intake of milk products on the antioxidant status of the consumer. A few studies performed in adults and premature infants are reviewed and it is stated that too little information is available to make any firm conclusions in this regard. Finally, a high interest has been devoted to the possible interference of milk with the antioxidant properties of flavonoid—rich food like tea. Most in vitro studies show an inhibition by milk on tea flavonoid activity whereas the results from the corresponding in vivo studies are equivocal. Our general conclusion is that several compounds in various milk fractions contribute to the antioxidant capacity of milk and that much further work is needed to unravel the complex interactions among the pro— and antioxidants, and their putative health effects on the consumer

The responses of HT22 cells to the blockade of mitochondrial complexes and potential protective effect of selenium supplementation

<p>Mitochondria are the major reactive oxygen species (ROS) &#8211; generating sites in mammalian cells. Blockade of complexes in the electron transport chain (ETC) increases the leakage of single electrons to O₂ and therefore increases ROS levels. Complexes I and III have been reported to be the major ROS-generating sites in mitochondria. In this study, using mouse hippocampal HT22 cells as in vitro model, we monitored the change of intracellular ROS level in response to the blockade of ETC at different complex, and measured changes of gene expression of antioxidant enzymes and phase II enzymes, also evaluated potential protective effect of selenium (Se) supplementation to the cells under this oxidative stress. In summary, our results showed that complex I was the major ROS-generating site in HT22 cells. Complex I blockade upregulated the mRNA levels of glutamylcysteine synthetase heavy and light chains, glutathione-S-transferases omega1 and alpha 2, hemoxygenase 1, thioredoxin reductase 1, and selenoprotein H. Unexpectedly, the expression of the enzymes that directly scavenge ROS decreased, including superoxide dismutases 1 and 2, glutathione peroxidase 1, and catalase. Se supplementation increased glutathione levels and glutathione peroxidase activity, indicating a potential protective role in oxidative stress caused by ETC blockade.</p